Present integrated circuits, such as solar cells for a solar panel, are currently manufactured by a process wherein a metal paste is applied to a substrate, and the entire assembly is heated in order to fuse, melt or sinter the metal particles in the paste and thereby create the desired circuitry. A sufficient amount of energy is applied to heat both the metal paste and the substrate up to the melting/sintering temperature of the metal. Beneficial interaction between the substrate and conducting material occurs at these high temperatures, but prolonged interaction decreases performance due to substrate damage and/or substrate property changes.
The limits in heating and cooling rate are normally governed by the heat power transfer to the total substrate with the metal paste. Conventionally, the total heat capacity of a substrate and metal needs to be considered to calculate a temperature increase for a given power input per second, and the heat capacity of, for example, a silicon substrate, is much larger than the heat capacity of the metal paste, e.g. a silver paste, arranged on the substrate. This heat capacity ratio ensures that much more power is needed, using the conventional methods, to get the same temperature increase over the same time period as if the metal were heated alone.
DE 100 41 889 A discloses a procedure for thermally changing the electrical properties of a semi-conducting coating material.
DE 102006005026A discloses an electrically conductive coating of sintered particles on a glass substrate. The sintered particles disclosed are nano-particles of ITO. The glass and ITO are heated capacitively in a resonant cavity using microwaves between 300 MHz and 30 GHz.
US Patent Publication 2005/0087226 discloses an electrode-arranging method for thin films on non-flat substrates. The method uses inductive heating in the range of several kHz to 1 MHz, which requires highly conductive, pre-sintered materials. The substrate and electrode material are both heated to the eutectic temperature of the substrate and electrode material.